This is believed to be an insim bug and related to old setups, an option long since removed from the low end cars prior to patch X, when set, seems to tell insim that it has passengers on board. I need to make Scawen aware of this actually but I dont have an effected set, if you could post the link here please i'll be able to diagnose it when the launch fever is over and present a bug report to Scawen. For now i'm affraid you'll have to use a different setup.